/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.sinosoft.monitor.org.objectweb.asm.commons;

import java.io.ByteArrayOutputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;

import com.sinosoft.monitor.org.objectweb.asm.ClassVisitor;
import com.sinosoft.monitor.org.objectweb.asm.FieldVisitor;
import com.sinosoft.monitor.org.objectweb.asm.MethodVisitor;
import com.sinosoft.monitor.org.objectweb.asm.Opcodes;

/**
 * A {@link ClassVisitor} that adds a serial version unique identifier to a
 * class if missing. Here is typical usage of this class:
 * <p/>
 * <pre>
 *   ClassWriter cw = new ClassWriter(...);
 *   ClassVisitor sv = new SerialVersionUIDAdder(cw);
 *   ClassVisitor ca = new MyClassAdapter(sv);
 *   new ClassReader(orginalClass).accept(ca, false);
 * </pre>
 * <p/>
 * The SVUID algorithm can be found <a href=
 * "http://java.sun.com/j2se/1.4.2/docs/guide/serialization/spec/class.html"
 * >http://java.sun.com/j2se/1.4.2/docs/guide/serialization/spec/class.html</a>:
 * <p/>
 * <pre>
 * The serialVersionUID is computed using the signature of a stream of bytes
 * that reflect the class definition. The National Institute of Standards and
 * Technology (NIST) Secure Hash Algorithm (SHA-1) is used to compute a
 * signature for the stream. The first two 32-bit quantities are used to form a
 * 64-bit hash. A java.lang.DataOutputStream is used to convert primitive data
 * types to a sequence of bytes. The values input to the stream are defined by
 * the Java Virtual Machine (VM) specification for classes.
 *
 * The sequence of items in the stream is as follows:
 *
 * 1. The class name written using UTF encoding.
 * 2. The class modifiers written as a 32-bit integer.
 * 3. The name of each interface sorted by name written using UTF encoding.
 * 4. For each field of the class sorted by field name (except private static
 * and private transient fields):
 * 1. The name of the field in UTF encoding.
 * 2. The modifiers of the field written as a 32-bit integer.
 * 3. The descriptor of the field in UTF encoding
 * 5. If a class initializer exists, write out the following:
 * 1. The name of the method, &lt;clinit&gt;, in UTF encoding.
 * 2. The modifier of the method, java.lang.reflect.Modifier.STATIC,
 * written as a 32-bit integer.
 * 3. The descriptor of the method, ()V, in UTF encoding.
 * 6. For each non-private constructor sorted by method name and signature:
 * 1. The name of the method, &lt;init&gt;, in UTF encoding.
 * 2. The modifiers of the method written as a 32-bit integer.
 * 3. The descriptor of the method in UTF encoding.
 * 7. For each non-private method sorted by method name and signature:
 * 1. The name of the method in UTF encoding.
 * 2. The modifiers of the method written as a 32-bit integer.
 * 3. The descriptor of the method in UTF encoding.
 * 8. The SHA-1 algorithm is executed on the stream of bytes produced by
 * DataOutputStream and produces five 32-bit values sha[0..4].
 *
 * 9. The hash value is assembled from the first and second 32-bit values of
 * the SHA-1 message digest. If the result of the message digest, the five
 * 32-bit words H0 H1 H2 H3 H4, is in an array of five int values named
 * sha, the hash value would be computed as follows:
 *
 * long hash = ((sha[0] &gt;&gt;&gt; 24) &amp; 0xFF) |
 * ((sha[0] &gt;&gt;&gt; 16) &amp; 0xFF) &lt;&lt; 8 |
 * ((sha[0] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 16 |
 * ((sha[0] &gt;&gt;&gt; 0) &amp; 0xFF) &lt;&lt; 24 |
 * ((sha[1] &gt;&gt;&gt; 24) &amp; 0xFF) &lt;&lt; 32 |
 * ((sha[1] &gt;&gt;&gt; 16) &amp; 0xFF) &lt;&lt; 40 |
 * ((sha[1] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 48 |
 * ((sha[1] &gt;&gt;&gt; 0) &amp; 0xFF) &lt;&lt; 56;
 * </pre>
 *
 * @author Rajendra Inamdar, Vishal Vishnoi
 */
public class SerialVersionUIDAdder extends ClassVisitor {

	/**
	 * Flag that indicates if we need to compute SVUID.
	 */
	private boolean computeSVUID;

	/**
	 * Set to true if the class already has SVUID.
	 */
	private boolean hasSVUID;

	/**
	 * Classes access flags.
	 */
	private int access;

	/**
	 * Internal name of the class
	 */
	private String name;

	/**
	 * Interfaces implemented by the class.
	 */
	private String[] interfaces;

	/**
	 * Collection of fields. (except private static and private transient
	 * fields)
	 */
	private Collection<Item> svuidFields;

	/**
	 * Set to true if the class has static initializer.
	 */
	private boolean hasStaticInitializer;

	/**
	 * Collection of non-private constructors.
	 */
	private Collection<Item> svuidConstructors;

	/**
	 * Collection of non-private methods.
	 */
	private Collection<Item> svuidMethods;

	/**
	 * Creates a new {@link com.sinosoft.monitor.com.sinosoft.monitor.org.objectweb.asm.commons.SerialVersionUIDAdder}. <i>Subclasses must not use
	 * this constructor</i>. Instead, they must use the
	 * {@link #SerialVersionUIDAdder(int, ClassVisitor)} version.
	 *
	 * @param cv a {@link ClassVisitor} to which this visitor will delegate
	 *           calls.
	 */
	public SerialVersionUIDAdder(final ClassVisitor cv) {
		this(Opcodes.ASM4, cv);
	}

	/**
	 * Creates a new {@link com.sinosoft.monitor.com.sinosoft.monitor.org.objectweb.asm.commons.SerialVersionUIDAdder}.
	 *
	 * @param api the ASM API version implemented by this visitor. Must be one
	 *            of {@link Opcodes#ASM4}.
	 * @param cv  a {@link ClassVisitor} to which this visitor will delegate
	 *            calls.
	 */
	protected SerialVersionUIDAdder(final int api, final ClassVisitor cv) {
		super(api, cv);
		svuidFields = new ArrayList<Item>();
		svuidConstructors = new ArrayList<Item>();
		svuidMethods = new ArrayList<Item>();
	}

	// ------------------------------------------------------------------------
	// Overriden methods
	// ------------------------------------------------------------------------

	/*
	 * Visit class header and get class name, access , and interfaces
	 * information (step 1,2, and 3) for SVUID computation.
	 */
	@Override
	public void visit(final int version, final int access, final String name,
	                  final String signature, final String superName,
	                  final String[] interfaces) {
		computeSVUID = (access & Opcodes.ACC_INTERFACE) == 0;

		if (computeSVUID) {
			this.name = name;
			this.access = access;
			this.interfaces = interfaces;
		}

		super.visit(version, access, name, signature, superName, interfaces);
	}

	/*
	 * Visit the methods and get constructor and method information (step 5 and
	 * 7). Also determine if there is a class initializer (step 6).
	 */
	@Override
	public MethodVisitor visitMethod(final int access, final String name,
	                                 final String desc, final String signature, final String[] exceptions) {
		if (computeSVUID) {
			if ("<clinit>".equals(name)) {
				hasStaticInitializer = true;
			}
		    /*
             * Remembers non private constructors and methods for SVUID
             * computation For constructor and method modifiers, only the
             * ACC_PUBLIC, ACC_PRIVATE, ACC_PROTECTED, ACC_STATIC, ACC_FINAL,
             * ACC_SYNCHRONIZED, ACC_NATIVE, ACC_ABSTRACT and ACC_STRICT flags
             * are used.
             */
			int mods = access
					& (Opcodes.ACC_PUBLIC | Opcodes.ACC_PRIVATE
					| Opcodes.ACC_PROTECTED | Opcodes.ACC_STATIC
					| Opcodes.ACC_FINAL | Opcodes.ACC_SYNCHRONIZED
					| Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT | Opcodes.ACC_STRICT);

			// all non private methods
			if ((access & Opcodes.ACC_PRIVATE) == 0) {
				if ("<init>".equals(name)) {
					svuidConstructors.add(new Item(name, mods, desc));
				} else if (!"<clinit>".equals(name)) {
					svuidMethods.add(new Item(name, mods, desc));
				}
			}
		}

		return super.visitMethod(access, name, desc, signature, exceptions);
	}

	/*
	 * Gets class field information for step 4 of the algorithm. Also determines
	 * if the class already has a SVUID.
	 */
	@Override
	public FieldVisitor visitField(final int access, final String name,
	                               final String desc, final String signature, final Object value) {
		if (computeSVUID) {
			if ("serialVersionUID".equals(name)) {
				// since the class already has SVUID, we won't be computing it.
				computeSVUID = false;
				hasSVUID = true;
			}
            /*
             * Remember field for SVUID computation For field modifiers, only
             * the ACC_PUBLIC, ACC_PRIVATE, ACC_PROTECTED, ACC_STATIC,
             * ACC_FINAL, ACC_VOLATILE, and ACC_TRANSIENT flags are used when
             * computing serialVersionUID values.
             */
			if ((access & Opcodes.ACC_PRIVATE) == 0
					|| (access & (Opcodes.ACC_STATIC | Opcodes.ACC_TRANSIENT)) == 0) {
				int mods = access
						& (Opcodes.ACC_PUBLIC | Opcodes.ACC_PRIVATE
						| Opcodes.ACC_PROTECTED | Opcodes.ACC_STATIC
						| Opcodes.ACC_FINAL | Opcodes.ACC_VOLATILE | Opcodes.ACC_TRANSIENT);
				svuidFields.add(new Item(name, mods, desc));
			}
		}

		return super.visitField(access, name, desc, signature, value);
	}

	/**
	 * Handle a bizarre special case. Nested classes (static classes declared
	 * inside another class) that are protected have their access bit set to
	 * public in their class files to deal with some odd reflection situation.
	 * Our SVUID computation must do as the JVM does and ignore access bits in
	 * the class file in favor of the access bits InnerClass attribute.
	 */
	@Override
	public void visitInnerClass(final String aname, final String outerName,
	                            final String innerName, final int attr_access) {
		if ((name != null) && name.equals(aname)) {
			this.access = attr_access;
		}
		super.visitInnerClass(aname, outerName, innerName, attr_access);
	}

	/*
	 * Add the SVUID if class doesn't have one
	 */
	@Override
	public void visitEnd() {
		// compute SVUID and add it to the class
		if (computeSVUID && !hasSVUID) {
			try {
				addSVUID(computeSVUID());
			} catch (Throwable e) {
				throw new RuntimeException("Error while computing SVUID for "
						+ name, e);
			}
		}

		super.visitEnd();
	}

	// ------------------------------------------------------------------------
	// Utility methods
	// ------------------------------------------------------------------------

	/**
	 * Returns true if the class already has a SVUID field. The result of this
	 * method is only valid when visitEnd is or has been called.
	 *
	 * @return true if the class already has a SVUID field.
	 */
	public boolean hasSVUID() {
		return hasSVUID;
	}

	protected void addSVUID(long svuid) {
		FieldVisitor fv = super.visitField(Opcodes.ACC_FINAL
				+ Opcodes.ACC_STATIC, "serialVersionUID", "J", null, new Long(
				svuid));
		if (fv != null) {
			fv.visitEnd();
		}
	}

	/**
	 * Computes and returns the value of SVUID.
	 *
	 * @return Returns the serial version UID
	 * @throws java.io.IOException if an I/O error occurs
	 */
	protected long computeSVUID() throws IOException {
		ByteArrayOutputStream bos;
		DataOutputStream dos = null;
		long svuid = 0;

		try {
			bos = new ByteArrayOutputStream();
			dos = new DataOutputStream(bos);

            /*
             * 1. The class name written using UTF encoding.
             */
			dos.writeUTF(name.replace('/', '.'));

            /*
             * 2. The class modifiers written as a 32-bit integer.
             */
			dos.writeInt(access
					& (Opcodes.ACC_PUBLIC | Opcodes.ACC_FINAL
					| Opcodes.ACC_INTERFACE | Opcodes.ACC_ABSTRACT));

            /*
             * 3. The name of each interface sorted by name written using UTF
             * encoding.
             */
			Arrays.sort(interfaces);
			for (int i = 0; i < interfaces.length; i++) {
				dos.writeUTF(interfaces[i].replace('/', '.'));
			}

            /*
             * 4. For each field of the class sorted by field name (except
             * private static and private transient fields):
             * 
             * 1. The name of the field in UTF encoding. 2. The modifiers of the
             * field written as a 32-bit integer. 3. The descriptor of the field
             * in UTF encoding
             * 
             * Note that field signatures are not dot separated. Method and
             * constructor signatures are dot separated. Go figure...
             */
			writeItems(svuidFields, dos, false);

            /*
             * 5. If a class initializer exists, write out the following: 1. The
             * name of the method, <clinit>, in UTF encoding. 2. The modifier of
             * the method, java.lang.reflect.Modifier.STATIC, written as a
             * 32-bit integer. 3. The descriptor of the method, ()V, in UTF
             * encoding.
             */
			if (hasStaticInitializer) {
				dos.writeUTF("<clinit>");
				dos.writeInt(Opcodes.ACC_STATIC);
				dos.writeUTF("()V");
			} // if..

            /*
             * 6. For each non-private constructor sorted by method name and
             * signature: 1. The name of the method, <init>, in UTF encoding. 2.
             * The modifiers of the method written as a 32-bit integer. 3. The
             * descriptor of the method in UTF encoding.
             */
			writeItems(svuidConstructors, dos, true);

            /*
             * 7. For each non-private method sorted by method name and
             * signature: 1. The name of the method in UTF encoding. 2. The
             * modifiers of the method written as a 32-bit integer. 3. The
             * descriptor of the method in UTF encoding.
             */
			writeItems(svuidMethods, dos, true);

			dos.flush();

            /*
             * 8. The SHA-1 algorithm is executed on the stream of bytes
             * produced by DataOutputStream and produces five 32-bit values
             * sha[0..4].
             */
			byte[] hashBytes = computeSHAdigest(bos.toByteArray());

            /*
             * 9. The hash value is assembled from the first and second 32-bit
             * values of the SHA-1 message digest. If the result of the message
             * digest, the five 32-bit words H0 H1 H2 H3 H4, is in an array of
             * five int values named sha, the hash value would be computed as
             * follows:
             * 
             * long hash = ((sha[0] >>> 24) & 0xFF) | ((sha[0] >>> 16) & 0xFF)
             * << 8 | ((sha[0] >>> 8) & 0xFF) << 16 | ((sha[0] >>> 0) & 0xFF) <<
             * 24 | ((sha[1] >>> 24) & 0xFF) << 32 | ((sha[1] >>> 16) & 0xFF) <<
             * 40 | ((sha[1] >>> 8) & 0xFF) << 48 | ((sha[1] >>> 0) & 0xFF) <<
             * 56;
             */
			for (int i = Math.min(hashBytes.length, 8) - 1; i >= 0; i--) {
				svuid = (svuid << 8) | (hashBytes[i] & 0xFF);
			}
		} finally {
			// close the stream (if open)
			if (dos != null) {
				dos.close();
			}
		}

		return svuid;
	}

	/**
	 * Returns the SHA-1 message digest of the given value.
	 *
	 * @param value the value whose SHA message digest must be computed.
	 * @return the SHA-1 message digest of the given value.
	 */
	protected byte[] computeSHAdigest(final byte[] value) {
		try {
			return MessageDigest.getInstance("SHA").digest(value);
		} catch (Exception e) {
			throw new UnsupportedOperationException(e.toString());
		}
	}

	/**
	 * Sorts the items in the collection and writes it to the data output stream
	 *
	 * @param itemCollection collection of items
	 * @param dos            a <code>DataOutputStream</code> value
	 * @param dotted         a <code>boolean</code> value
	 * @throws java.io.IOException if an error occurs
	 */
	private static void writeItems(final Collection<Item> itemCollection,
	                               final DataOutput dos, final boolean dotted) throws IOException {
		int size = itemCollection.size();
		Item[] items = itemCollection.toArray(new Item[size]);
		Arrays.sort(items);
		for (int i = 0; i < size; i++) {
			dos.writeUTF(items[i].name);
			dos.writeInt(items[i].access);
			dos.writeUTF(dotted ? items[i].desc.replace('/', '.')
					: items[i].desc);
		}
	}

	// ------------------------------------------------------------------------
	// Inner classes
	// ------------------------------------------------------------------------

	private static class Item implements Comparable<Item> {

		final String name;

		final int access;

		final String desc;

		Item(final String name, final int access, final String desc) {
			this.name = name;
			this.access = access;
			this.desc = desc;
		}

		public int compareTo(final Item other) {
			int retVal = name.compareTo(other.name);
			if (retVal == 0) {
				retVal = desc.compareTo(other.desc);
			}
			return retVal;
		}

		@Override
		public boolean equals(final Object o) {
			if (o instanceof Item) {
				return compareTo((Item) o) == 0;
			}
			return false;
		}

		@Override
		public int hashCode() {
			return (name + desc).hashCode();
		}
	}
}
